Leica CF 22 Notice D'utilisation page 38

Conditioning the flash capacitor
For technical reasons, it is important to switch
on the flash unit once every three months for
about 10 minutes (the capacitor installed in the
flash unit undergoes physical change if the
device is not operated for a prolonged period).
The batteries must at least provide enough
power so that the flash-ready indication lights
up not later than 1 minute after switching on.
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